1. Field of Invention
The present invention relates to a vision correction system and an operating method thereof, and more particularly to the technology of using a laser unit for performing a treatment on an eyeball of a person to form a correction area and a prevention area on the eyeball, so as to correct vision, but also solve a presbyopia problem occurring as eyeball functions degenerate.
2. Related Art
Referring to FIG. 1, the process in which a normal human eye receives light and generates an image is usually as follows. The light is refracted by the cornea 2 and passes through a pupil 3 of an eyeball 1. By the function of an iris 5, the pupil 3 dilates or constricts to regulate the amount of incoming light. Then, a crystalline lens 4 of the eyeball 1 refracts the light to focus images on a retina 6, and the images are transmitted to the brain via an optic nerve 7. The spherical curvature of the cornea 2 is very important, because ⅔ of eyes' focusing is achieved by the cornea 2. If the cornea 2 functions normally, it can refract light correctly to allow images to focus clearly on the retina 6. However, if the cornea 2 or the crystalline lens 4 fails to regulate light properly, a blurry vision will occur as images no longer focus correctly on the retina 6.
Referring to FIG. 2, the cornea 2 shown in FIG. 2 has a larger spherical curvature than that of the normal cornea 2, so that the cornea 2 refracts the entering light to focus in front of the retina 6. As a result, distant object images cannot be seen clearly, which is usually called myopia. Referring to FIG. 3, the cornea 2 shown in FIG. 3 has a smaller spherical curvature than that of the normal cornea 2, so that the cornea 2 refracts the entering light to focus behind the retina 6. As a result, nearby object images cannot be seen clearly, which is usually called hyperopia. In addition, referring to FIG. 4, a non-uniform spherical curvature of the cornea 2 shown in FIG. 4 causes astigmatism result in the inability to focus clearly at any distance.
In addition to the above problems caused by the spherical curvature of the cornea, when the elasticity of the crystalline lens of the eye gradually decreases or the contraction ability of the ciliary muscles deteriorates with age, the focusing ability of the eyeball becomes poorer and causes nearby objects to look blurry, which is called presbyopia. Moreover, when people with myopia getting older, they are still susceptible to presbyopia because of degeneration of their eye functions.
All the abovementioned diseases resulting from abnormal focusing in the eyes are generally referred to as refractive errors. In order to improve the focusing function, such refractive errors can now be treated through an excimer laser surgery in addition to the conventional correction methods such as wearing glasses or contact lenses. Since its success in the former Soviet Union more than 40 years ago, the excimer laser refractive surgery for refractive errors has been developed from the original radial keratotomy (RK) and photorefractive keratectomy (PRK) correction methods to the laser assisted in-situ keratomileusis (LASIK) technology which combines advantages of the RK and PRK surgeries. The new surgery method is safer and more effective, and provides patients with a fast and convenient post-surgery operation. However, with more and more patients with refractive errors receiving the laser surgery, the safety concerns vanish gradually, and the new generation laser surgery has currently become the main option for vision correction treatment as the operation time is reduced, the safety is higher, and the post-surgery treatment is simpler. The number of patients with the refractive errors receiving the LASIK surgery in the U.S. alone was as high as 2.5 million in 2007.
Referring to FIG. 5, laser beam is used to vaporize and remove a thin layer of tissues in the center of the cornea 2 so as to flatten the radian of the center of the cornea, thereby achieving the purpose of correcting myopia by correcting dioptric imaging of the light. The surgery method is capable to correct myopia of dioptric values ranging from −1.0 to −20.0 without reducing the robustness of the eyeballs or producing sequelae such as nyctalopia and hemeralopia, thereby significantly increasing the safety and precision of myopia correction. Besides, the surgery method is also applicable to the correction of hyperopia and astigmatism.
People receiving such surgery may well expect a life time of improved eyesight without wearing glasses in the following five to ten years; however, the modulation of their eyeballs still degenerates due to age, and presbyopia is increased and the same as hyperopia and astigmatism.
In addition to correction surgeries performed on patients with myopia, corrective treatment applicable to patients with hyperopia and astigmatism has been developed currently. In spite of outstanding achievements in treatment of the refraction error of myopia, the laser refractive treatment for refractive errors faces a lot of challenges in refractive error correction of presbyopia.